Damascene copper electroplating for on-chip interconnections, a process that we conceived and developed in the early 1990s, makes it possible to fill submicron trenches and vias with copper without creating a void or a seam and has thus proven superior to other technologies of copper deposition. We discuss here the relationship of additives in the plating bath to superfilling, the phenomenon that results in superconformal coverage, and we present a numerical model which accounts for the experimentally observed profile evolution of the plated metal.

Damascene copper electroplating for chip interconnections

Since the automation of the electron backscatter diffraction (EBSD) technique, EBSD systems have become commonplace in microscopy facilities within materials science and geology research laboratories around the world. The acceptance of the technique is primarily due to the capability of EBSD to aid the research scientist in understanding the crystallographic aspects of microstructure. There has been considerable interest in using EBSD to quantify strain at the submicron scale. To apply EBSD to the characterization of strain, it is important to understand what is practically possible and the underlying assumptions and limitations. This work reviews the current state of technology in terms of strain analysis using EBSD. First, the effects of both elastic and plastic strain on individual EBSD patterns will be considered. Second, the use of EBSD maps for characterizing plastic strain will be explored. Both the potential of the technique and its limitations will be discussed along with the sensitivity of various calculation and mapping parameters.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1431927611000055

A review of strain analysis using electron backscatter diffraction.

High-resolution elastic strain measurement from electron backscatter diffraction patterns: New levels of sensitivity

Vascular stenosis triggers adaptive cellular responses that induce adverse remodeling, which can progress to partial or complete vessel occlusion. Despite its severity, cellular interactions and biophysical cues that regulate pathological progression are poorly understood. We report the design and fabrication of a three-dimensional in vitro system to model vascular stenosis so that specific cellular interactions and responses to hemodynamic stimuli can be investigated. Tubular cellularized constructs (cytotubes) were produced using a collagen casting system to generate a stenotic arterial model. Fabrication methods were developed to create cytotubes containing co-cultured vascular cells, where cell viability, distribution, morphology, and contraction were examined (Figure). Fibroblasts, bone marrow primary cells, smooth muscle cells (SMCs), and endothelial cells (ECs) remained viable during culture and developed locationand time-dependent morphologies. We found cytotube contraction to depend on cellular composition, where SMC-EC co-cultures adopted intermediate contractile phenotypes between SMCand EC-only cytotubes. Our fabrication approach and resulting artery model can serve as an in vitro 3D culture system to investigate vascular pathogenesis.

Microscopy and Microanalysis

Copper wires were prepared in a silicon oxide matrix using the methods of semiconductor manufacturing and were electrically characterized. The width of the smallest structure was 40 nm and of the largest, 1000 nm; the heights were 50, 155, and 230 nm. Many samples of each size have been measured in order to perform a systematic investigation. The resistivity of the sample was extracted using the temperature coefficient of resistance. A significant increase in the resistivity was found for the small structures (roughly a factor 2 for 50-nm width). A model based on physical parameters was used in the analysis of the electrical data and very good agreement was obtained. The sensitivity of the various model parameters obtained by a best-fit procedure to the experimental data has been investigated. The impact of width and height on the resistivity, the influence of electron scattering at grain boundaries compared to surface scattering, and the impact of grain sizes and impurities will be discussed in detail.

Comprehensive study of the resistivity of copper wires with lateral dimensions of 100 nm and smaller

Summary


The spatial resolution of electron diffraction within the scanning electron microscope (SEM) has progressed from channelling methods capable of measuring crystallographic characteristics from 10 μm regions to electron backscatter diffraction (EBSD) methods capable of measuring 120 nm particles Here, we report a new form of low-energy transmission Kikuchi diffraction, performed in the SEM Transmission-EBSD (t-EBSD) makes use of an EBSD detector and software to capture and analyse the angular intensity variation in large-angle forward scattering of electrons in transmission, without postspecimen coils We collected t-EBSD patterns from Fe–Co nanoparticles of diameter 10 nm and from 40 nm-thick Ni films with in-plane grain size 15 nm The patterns exhibited contrast similar to that seen in EBSD, but are formed in transmission Monte Carlo scattering simulations showed that in addition to the order of magnitude improvement in spatial resolution from isolated particles, the energy width of the scattered electrons in t-EBSD is nearly two orders of magnitude narrower than that of conventional EBSD This new low-energy transmission diffraction approach builds upon recent progress in achieving unprecedented levels of imaging resolution for materials characterization in the SEM by adding high-spatial-resolution analytical capabilities

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Transmission EBSD from 10 nm domains in a scanning electron microscope

Tensile properties of free-standing aluminum thin films☆

An experimental method is described for performing thermal fatigue testing of thin films and lines on substrates. The method uses Joule heating from alternating currents to generate temperature, strain, and stress cycles in the metal structures. The apparatus has been installed in a scanning electron microscope and allows in situ observations of the fatigue damage evolution. First observations on Cu films reveal that fatigue damage forms in submicrometer thick films and is strongly affected by the film thickness and grain size. In addition, results from a special test structure confirm that the damage is caused by fatigue and not by electromigration.

Thermal fatigue testing of thin metal films

We have studied tensile deformation and crack growth behavior of free-standing, electron beam evaporated copper films suspended over windows etched in a silicon substrate. In-situ straining experiments were performed on these films using a transmission electron microscope. External tests were conducted on a piezoelectric-driven microtensile system. Macroscopically, these copper films exhibited very low ductility (

Robert R. Keller

Papers

Transmission EBSD from 10 nm domains in a scanning electron microscope

Tensile properties of free-standing aluminum thin films☆

Thermal fatigue testing of thin metal films

Tensile and fracture behavior of free-standing copper films

Characterization of interfacial dislocation networks in a creep-deformed nickel-base superalloy